This invention relates to a new mixing system, and more particularly to a new apparatus and a new method for more intimately mixing a premix or preliminary mixture of materials, especially polymeric materials.
The teachings of the invention are especially useful for the shear mixing of polymeric materials. Shear mixing is a highly dispersive type of mixing. It is to be distinguished from distributive mixing which commonly consists of stirring powdery ingredients or materials together. Highly efficient shear mixing effectively converts a distributive mixture into one exhibiting more or less uniform properties throughout the mass thereof, whereas in a distributive mixture the individual component properties are usually quite evident when the distributive mixture is subjected to testing.
Significant value and benefits arise from converting a premix of relatively distributive character into a shear mixed mass, and this is especially evident in the polymeric or plastics art. The dispersive effects of shear mixing are frequently desired to provide an improved and uniform quality for a polymer or mixture of polymers mixed with other materials or ingredients such as plasticizers, extenders, curing or cross-linking agents, and almost any other component or ingredient (even pigments) as those of skill in polymer compounding art may desire. Effective shear mixing reaches down to the molecular level, pulling and stretching polymeric molecules and parts and intertwining them with other components of the mass being shear mixed.
While the invention is especially useful for shear mixing, it should be understood that the teachings of this invention are not solely limited to shear mixing. Further, they are not solely limited to the most efficient shear mixing of which they are capable. It is a fair statement however to say that the teachings of the invention are directed to apparatus and methods for more intimately mixing ingredients or materials, usually and preferably with some type of shearing action.
It is also acknowledged that shear mixing of polymer masses as such is old technology. However, insofar as is known, the apparatus and methods employed in shear mixing as heretofore conducted are vastly different from the apparatus and methods of this invention. Heretofore known commercially available shear mixing apparatus is relatively complex and expensive. It is useful for large volume shear mixing, but not for the shear mixing of laboratory quantities for experimental or test purposes. Known apparatus designed especially for laboratory shear mixing is relatively expensive (about six figures in cost), and effective use of it still requires a relatively large quantity of material for treatment. Much desired has been a relatively economical and effective shear mixing apparatus and methods capable of scaled down economical laboratory shear mixing for low gram quantities as well as for somewhat larger laboratory quantities as experimental progress is made. It is to a solution of this problem that this invention is primarily directed.
A very significant benefit of the invention making it especially valuable for laboratory use is the ease by which apparatus of the invention can be dismantled and cleaned--using, of course, an appropriate solvent for the residuum of the polymeric mass to be washed away.